Cellulases are amongst the most widely used enzymes in industry. They are generally applied in textile industry, detergent industry, pulp and paper industry, feed and food industry, including baking and in hydrolysis of lignocellulosic material for, e.g., bioethanol production etc. The practical use of cellulases is hampered by the nature of the cellulase compositions, which often are enzyme mixtures having a variety of activities and substrate specificities. For this reason, efforts have been made to obtain cellulases having only the desired activities. The unique properties of each cellulase make some more suitable for certain purposes than others.
In fabric treatment cellulases attack the chains of cellulose molecules that form the cotton fibers, thereby affecting the characteristics of the fabric.
In textile industry a “stone washed” or abraded look has been denim producers' interest in recent years. Traditional stone washing with pumice stones reduces the strength of fabric and burdens the laundering apparatuses. The trend has been towards enzymatic denim finishing processes and cellulases have replaced or are being used together with pumice stones to give the fabric its desired “worn” look. Controlled enzyme treatments result in less damage to the garments and machines and eliminate the need for disposal of stones.
Additionally, textile industry uses cellulases in biofinishing, i.e. to create permanent improvement of depilling, and to improve pilling resistance, clear surface structure by reduced fuzz, improve textile handle, such as softness, smoothness and a silkier feel, improve drapability and brighter colors of the textile and improve moisture absorbability.
Cellulases comprise a catalytic domain/core (CD) expressing cellulase activity. In addition to the catalytic domain the cellulase molecule may comprise one or more cellulose binding domains (CBDs), also named as carbohydrate binding domains/modules (CBD/CBM), which can be located either at the N- or C-terminus of the catalytic domain. CBDs have carbohydratebinding activity and they facilitate the enzymatic action on solid substrates. The catalytic core and the CBD are typically connected via a flexible and highly glycosylated linker region.
Cellulases that attack primarily on the surface of the fiber are especially useful in stone washing of denim dyed with Indigo dye, as the dye is located on the surface of the fiber. Cellulases applied in denim treatment are usually divided into two main groups: acid and neutral cellulases. Acid cellulases typically operate at pH 4.0-5.5 and the neutral cellulases in the range of pH 6-8. Acid cellulases are especially used in biofinishing (depilling) and also in denim treatment (biostoning) while neutral celluases are typically used in denim applications.
Endoglucanases (EGs) are one of the three types of cellulases generally needed for the biological conversion of cellulose to glucose. Some naturally occurring endoglucanases have a cellulose-binding domain (CBD), while others do not. Endoglucanases are widely used in textile, detergent, bioethanol and pulp and paper industry.
Cellulases including endoglucanases may be classified into various glycosyl hydrolase families according their primary sequence, supported by analysis of the three dimensional structure of some members of the family (Henrissat 1991, Henrissat and Bairoch 1993, 1996). For example glycosyl hydrolase families 5, 7, 12 and 45 contain endoglucanases. Most of the acid textile cellulases belong to family 5, whereas most of the neutral textile cellulases are of family 12 or 45.
The wide spectrum of industrial uses for endoglucanases has established a need for commercial endoglucanase products showing desired performance at desired conditions such as pH and temperature ranges.
The majority of the industrially used enzymes work better at elevated temperatures, usually about >50° C., but for energy saving reasons, better color fastness and reduction of shrinkage of garments there is a need for enzymes with good performance at lower temperature levels i.e. <50° C., for example about 30 to 40° C., or even 20 to 40° C. Such cold active enzymes have been described e.g. in bacteria, especially in Bacillus. However, production of bacterial enzymes for industrial applications is complicated and laborious compared to the production of fungal enzymes. Still there is very little knowledge about possible cold active fungal endoglucanases.
To our knowledge no cold acting endoglucanase of family 45 has been described so far.
An endoglucanase of the Cel45 family is disclosed in U.S. Pat. No. 5,610,129, which describes dye transfer inhibiting compositions containing a Humicola insolens kd43 cellulase. Its thermal properties are not disclosed.
Gibberella zeae Cel45 enzymes have not been proposed to be used in textile finishing.
U.S. Pat. No. 7,256,032 describes Cel45 cellulases having good performance in textile finishing. Performance in denim finishing is optimal at 60° C., and the lowest temperature measured is 40° C. with less than 50% of the optimal activity.
US20071070003 describes cellulase preparations performing well e.g. in laundry compositions, biopolishing newly manufactured textiles and providing an abraded look for cellulosic fabric. None of the enzymes described shows an advantageous performance at low temperatures.
Thus there is a continuous need for new and advantageous cellulases having desired properties and thermal profiles. The present invention meets this need.